1. Field of the Invention
Embodiments of the present invention generally relate to voltage regulator circuits, and more specifically to a configurable low drop out regulator circuit.
2. Description of the Related Art
Many electronic systems include sets of circuitry that require one or more regulated voltage sources configured to generate specific respective voltages. For example, an electronic system may include a set of circuitry that requires a regulated voltage source of 1.2V, another set of circuitry that requires a regulated voltage source of 3.3V, and yet another set of circuitry that requires a regulated 5V voltage source. An electronic system may also require two distinct voltages sources of 1.2V in order to isolate sensitive circuits from noisy circuits. Each set of circuitry that requires a specific voltage may operate from a common voltage source, or from independent voltage sources that are configured to supply a nominally equivalent voltage. Each voltage source is also configured to source (or sink) a specific maximum current. For example, the 1.2V voltage source may be configured to source up to one ampere, while the 3.3V voltage source may be configured to source up to only 50 milliamps.
One popular type of voltage supply is a low drop out (LDO) regulator circuit or simply “LDO.” An LDO typically includes a voltage drop element disposed between a voltage source and an LDO output node, which supplies a system element with a specified voltage. Control circuitry within the LDO adjusts the voltage drop element in response to dynamic loading of the LDO output node to generate a constant voltage on the LDO output node. A conventional LDO is designed to use a specific voltage drop element that is disposed either on chip or off chip.
As electronic systems become more complex, each integrated circuit within a given system is typically designed to incorporate an increasing number of different system functions, including circuits that function as regulated voltage sources. LDOs are commonly used in this setting for low to moderate current applications. A multi-function integrated circuit typically includes a plurality of such voltage sources, wherein each voltage source is separately designed assuming a specific overall system configuration. For example, a system may require a certain number of low current voltage supplies and one or more high current voltage supplies. In this scenario, a multi-function integrated circuit may include a set of on-chip LDOs specifically configured to act as direct output regulators, capable of supplying low to modest current at a regulated voltage. The multi-function integrated circuit may also include one or more LDOs specifically configured to act as control regulators for an associated external transistor capable of supplying relatively high current. Each specifically optimized LDO represents a costly engineering effort and is conventionally designed to only operate in a specific mode. If the LDOs need to operate in a different mode than originally envisioned, then either a different multi-function integrated circuit needs to be developed and manufactured to implement the required set of LDOs or external power supplies need to be added to the system. Either option may add significant expense to the system.
As the foregoing illustrates, what is needed in the art is a configurable LDO circuit capable of adapting to changing system requirements without requiring a re-design.